A RhMOF catalyst for N2O catalytic decomposition and its preparation method

Abstract

This invention discloses a RhMOF catalyst for the catalytic decomposition of N2O and its preparation method, relating to the field of novel catalyst synthesis for nitrous oxide treatment. The preparation method of this invention includes the following steps: (1) mixing Nb2O5, HF solution, and deionized water; (2) adding squaric acid and RhCl3 to the solution obtained in step (1) at room temperature with stirring; (3) heating the reaction system obtained in step (2) at 120–140°C for 24–48 h, filtering the resulting solid, rinsing it with water and acetone at room temperature, and drying it to obtain the RhMOF catalyst. The RhMOF catalyst prepared by this invention can reduce the 100% decomposition temperature of N2O by about 250°C, greatly reducing the catalytic reaction temperature of Rh-based catalysts, and the preparation method is simple and easy to promote.

Description

Technical Field

[0001] This invention relates to the field of novel catalyst synthesis for nitrous oxide treatment, specifically to a RhMOF catalyst for the catalytic decomposition of N2O and its preparation method. Background Technology

[0002] Nitrous oxide (N2O), commonly known as laughing gas, is a dangerous gas primarily derived from industrial production, such as nitric acid production and the combustion of various chemical fuels. Nitrous oxide's harm to the atmosphere is twofold: it depletes the ozone layer and exacerbates the greenhouse effect. Nitrous oxide has a long atmospheric retention time and can be transported to the stratosphere, leading to ozone layer depletion, creating ozone holes, and exposing humans and other organisms to ultraviolet radiation from the sun, causing damage to human skin, eyes, and the immune system. Nitrous oxide is also one of the six greenhouse gases designated in the Kyoto Protocol. Its single-molecule warming potential is 298 times that of carbon dioxide, meaning its greenhouse effect is 298 times greater than that of carbon dioxide, placing it as the third largest greenhouse gas after carbon dioxide and methane. Therefore, developing novel low-temperature N2O catalysts for use in automobile exhaust treatment and flue gas treatment is beneficial for controlling greenhouse gas emissions.

[0003] Catalytic decomposition is a good option for eliminating N2O. Rh-based catalysts are common N2O decomposition catalysts. For example, patent application CN114618572A describes a catalyst in which any two of Fe, Ru, or Rh are impregnated onto a molecular sieve. The resulting catalyst achieves a 10% N2O conversion at a reaction temperature of 250°C and 100% N2O decomposition at 430°C. The background section further specifies that existing Rh-based catalysts generally require temperatures around 400°C to achieve 100% N2O conversion. Summary of the Invention

[0004] The present invention aims to provide a RhMOF catalyst for the catalytic decomposition of N2O and its preparation method, in order to further reduce the catalytic reaction temperature of existing Rh-based catalysts.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a RhMOF catalyst for the catalytic decomposition of N2O includes the following steps:

[0007] (1) Mix Nb2O5, HF solution and deionized water;

[0008] (2) At room temperature and under stirring, add squaric acid and RhCl3 to the solution obtained in step (1);

[0009] (3) The reaction system obtained in step (2) is heated at 120-140°C for 24-48 hours. The solid obtained by filtration is washed with water and acetone at room temperature and dried to obtain the RhMOF catalyst.

[0010] Preferably, the molar ratio of Nb2O5, HF, squaric acid and RhCl3 is 1:7.5:4:0.035.

[0011] The RhMOF catalyst prepared by the above method.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] The RhMOF catalyst prepared by this invention can reduce the 100% decomposition temperature of N2O by about 250°C, which greatly reduces the catalytic reaction temperature of Rh-based catalysts. Moreover, the preparation method is simple and easy to promote. Attached Figure Description

[0014] Figure 1 Line graph comparing the N2O catalytic decomposition activities of Rh-based catalysts with different supports;

[0015] Figure 2 Line graph comparing the N2O catalytic decomposition activities of catalysts with different active sites;

[0016] Figure 3 A bar chart comparing the effects of impurity gases on the N2O catalytic decomposition activity of different catalysts;

[0017] Figure 4 Line graph showing the change in N2O catalytic decomposition activity of different catalysts with the number of reactions;

[0018] Figure 5 Line graph comparing the N2O catalytic decomposition activities of catalysts with different Rh mass percentages. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described below in conjunction with various embodiments and accompanying drawings. The implementation of the present invention includes, but is not limited to, the following embodiments.

[0020] Throughout this specification, unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of any conflict, this specification shall prevail.

[0021] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0022] The following examples demonstrate the preparation of different catalysts under different reaction conditions and the verification of their catalytic activity.

[0023] Example 1

[0024] The preparation process of the catalyst in this embodiment is as follows:

[0025] (1) Mix 1 mmol (265 mg) of Nb2O5 and HF solution (48%, 1 mL, 7.15 mmol) with 10 mL of deionized water;

[0026] (2) Dissolve 4 mmol (456 mg) of squaric acid and 0.035 mmol (7.39 mg) of rhodium chloride RhCl3 in the above solution at room temperature by stirring.

[0027] (3) Place the above solution into a reaction vessel with a polytetrafluoroethylene liner and heat at 120-140°C for 24 hours.

[0028] (4) The solid obtained by filtration was washed three times with water and three times with acetone at room temperature, and then dried to obtain the RhMOF catalyst (Rh mass percentage is 0.5%).

[0029] Example 2

[0030] This embodiment explores the effect of different supports on activity: using the impregnation method, 0.5% Rh was loaded onto activated carbon, SBA-15 molecular sieve and Al2O3, and calcined in air at 550°C for 2 hours to obtain three catalysts: Rh / C, Rh / SBA-15 and Rh / Al2O3.

[0031] The RhMOF catalyst obtained in Example 1, along with the Rh / C, Rh / SBA-15, and Rh / Al2O3 catalysts obtained in this example, were used to test the catalyst activity for N2O decomposition according to the following method: 0.5 g of catalyst was loaded into a straight-tube quartz reactor with a diameter of 1 cm, and the reactor was heated to the target temperature for reaction. The gas flow rate at the reactor inlet was 200 mL / min, and the gas composition was 10% N2O and 90% N2. The composition of the gas after the reaction was analyzed using a mass spectrometer at the reactor outlet.

[0032] Get as Figure 1 The results show that, under the same low-temperature conditions, the catalytic activity of RhMOF is much higher than that of commercially available Rh / C, Rh / SBA-15 and Rh / Al2O3.

[0033] To investigate the effect of impurity gases on catalytic activity, the RhMOF catalyst obtained in Example 1, along with three other catalysts obtained in this example—Rh / C, Rh / SBA-15, and Rh / Al2O3—were used to test the catalyst activity for N2O decomposition. The following method was used: 0.5 g of catalyst was loaded into a straight-tube quartz reactor with a diameter of 1 cm, and the reactor was heated to the target temperature for reaction. The inlet gas flow rate was 200 mL / min, and the gas composition was 0.5% SO2, 9.5% N2O, and 90% N2. The composition of the gas after reaction was analyzed using a mass spectrometer at the reactor outlet. The results are shown below. Figure 3 As shown in the figure, except for the RhMOF catalyst, the catalytic activity of the Rh / SBA-15, Rh / C, and Rh / Al2O3 catalysts decreased after 10 hours of catalytic reaction under the influence of SO2 impurity gas, with the Rh / Al2O3 catalyst being less affected.

[0034] To investigate the stability of the catalysts, the catalytic stability of the RhMOF catalyst obtained in Example 1, along with the Rh / C, Rh / SBA-15, and Rh / Al2O3 catalysts obtained in this example, was tested at 250°C. After 100 hours of continuous experiments, the decomposition rates were recorded at 20 / 40 / 60 / 80 / 100 cycles. The results are as follows: Figure 4 As shown, the catalytic activity of RhMOF for N2O decomposition remains basically unchanged, and the N2O decomposition rate remains above 90%. After 100 hours of continuous experiment, the catalytic activity of Rh / C and Rh / Al2O3 catalysts did not decrease much, while the catalytic activity of Rh / SBA-15 decreased significantly after 100 hours of continuous experiment.

[0035] Example 3

[0036] This example explores the effect of different active centers (promoters) on catalytic activity: Based on Example 1, with other conditions unchanged, the same mass percentage of Rh was replaced with Ir, Fe, Co, and Ce to obtain four catalysts: IrMOF, FeMOF, CoMOF, and CeMOF.

[0037] The RhMOF catalyst obtained in Example 1, along with four other catalysts obtained in this example (IrMOF, FeMOF, CoMOF, and CeMOF), were used to test the activity of the catalysts for N2O decomposition according to the following method: 0.5 g of catalyst was loaded into a straight-tube quartz reactor with a diameter of 1 cm, and the reactor was heated to the target temperature for reaction. The gas flow rate at the reactor inlet was 200 mL / min, and the gas composition was 10% N2O and 90% N2. The composition of the gas after the reaction was analyzed using a mass spectrometer at the reactor outlet.

[0038] Get as Figure 2The results show that RhMOF exhibits the best catalytic activity, while IrMOF shows slightly lower activity. FeMOF, CoMOF, and CeMOF show relatively poor activity.

[0039] Example 4

[0040] This embodiment explores the effect of different Rh mass percentages on catalytic activity: RhCl3 was replaced with 1.48 mg, 4.43 mg, 7.39 mg, and 14.78 mg of Rh to obtain RhMOF catalysts with concentrations of 0.1%, 0.3%, 0.5%, and 1%. Figure 5 It can be seen that the catalytic activity of RhMOF increases with the increase of Rh loading. When the Rh loading is 0.5%, the catalytic activity of RhMOF reaches its maximum. Further increasing the Rh loading will decrease the catalytic activity.

[0041] The above embodiments are merely one of the preferred embodiments of the present invention and should not be used to limit the scope of protection of the present invention. Any modifications or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but solve the same technical problem as the present invention, should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a RhMOF catalyst for the catalytic decomposition of N2O, characterized in that, Includes the following steps: (1) Mix Nb2O5, HF solution and deionized water; (2) At room temperature and under stirring, add squaric acid and RhCl3 to the solution obtained in step (1); (3) The reaction system obtained in step (2) is heated at 120-140°C for 24-48 hours. The solid obtained by filtration is washed with water and acetone at room temperature and dried to obtain the RhMOF catalyst. In steps (1) and (2), the molar ratio of Nb2O5, HF, squaric acid and RhCl3 is 1:7.5:4:0.

035.

2. The RhMOF catalyst prepared by the preparation method according to claim 1.

3. The application of the RhMOF catalyst as described in claim 2 as a catalyst in the N2O catalytic decomposition reaction.

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